An Equation for the Flow of Blood, Plasma and Serum through Glass Capillaries

WHEN blood flows through narrow tubes, the larger suspended particles tend to accumulate in the centre, leaving a zone of plasma near the walls. In mammals, the red cells are smaller than the leucocytes but, when associated in groups (rouleaux or clumps), they will tend to replace the leucocytes in the centre, thus altering the distribution of concentration. This means that Poiseuille's fourth-power radius law fails to hold 1 . Several authors, notably Fåhraeus 2 , have stressed the importance of this in large and small vessels in vivo . The significance of intravascular clumping or ’sludging‘ has been widely discussed by Knisely and his school 3 (see also ref. 4).